Tuesday, September 19, 2017

Arguments from authority, and the Cladistic Ghost, in historical linguistics

Arguments from authority play an important role in our daily lives and our
societies. In political discussions, we often point to the opinion of trusted
authorities if we do not know enough about the matter at hand. In medicine,
favorable opinions by respected authorities function as one of four levels of evidence (admittedly, the
lowest) to judge the strength of a medicament. In advertising, the (at times
doubtful) authority of celebrities is used to convince us that a certain
product will change our lives.

Arguments from authority are useful, since they
allow us to have an opinion without fully understanding it. Given the
ever-increasing complexity of the world in which we live, we could not do
without them. We need to build on the opinions and conclusions of others in
order to construct our personal little realm of convictions and insights. This
is specifically important for scientific research, since it is based on
a huge network of trust in the correctness of previous studies which no single
researcher could check in a lifetime.

Arguments from authority are, however, also dangerous if we blindly trust
them without critical evaluation. To err is human, and there is no guarantee
that the analysis of our favorite authorities is always error proof. For example, famous
linguists, such as Ferdinand de Saussure
(1857-1913) or Antoine Meillet (1866-1936),
revolutionized the field of historical linguistics, and their theories had a
huge impact on the way we compare languages today. Nevertheless, this does not
mean that they were right in all their theories and analyses, and we should
never trust any theory or methodological principle only because it was
proposed by Meillet or Saussure.

Since people tend to avoid asking why their authority came to a certain
conclusion, arguments of authority can be easily abused. In the extreme, this
may accumulate in totalitarian societies, or societies ruled by religious
fanatism. To a smaller degree, we can also find this totalitarian attitude
in science, where researchers may end up blindly trusting
the theory of a certain authority without further critically investigating it.

The comparative method

The authority in this context does not necessarily need to be a real person, it can also be a theory or a certain methodology.
The financial crisis from 2008
can be taken as an example of a methodology, namely classical
"economic forecasting", that turned out to be trusted much more than it
deserved.
In historical linguistics, we have a similar quasi-religious attitude
towards our traditional comparative method (see Weiss 2014
for an overview), which we use in order to compare languages.
This "method" is in fact no method at all, but rather a huge bunch of
techniques by which linguists have been comparing and reconstructing
languages during the past 200 years.
These include the detection of cognate or "homologous" words across
languages, and the inference of regular sound correspondence patterns
(which I discussed in a blog from October last year),
but also the reconstruction of sounds and words of ancestral languages
not attested in written records, and the inference of the phylogeny of a
given language family.

In all of these matters, the comparative method enjoys a quasi-religious
authority in historical linguistics. Saying that they do not follow
the comparative method in their work is among the worst things you can
say to historical linguists. It hurts. We are conditioned from when we were small to
feel this pain. This is all the more surprising, given that scholars rarely
agree on the specifics of the methodology, as one can see from the
table below, where I compare the key tasks that different authors
attribute to the "method" in the literature. I think one can easily see
that there is not much of an overlap, nor a pattern.

Varying accounts on the "comparative methods" in the linguistic literature

It is difficult to tell how this attitude evolved. The foundations of the
comparative method go back to the early work of scholars in the 19th century,
who managed to demonstrate the genealogical relationship of the Indo-European languages.
Already in these early times, we can find hints regarding the "methodology"
of "comparative grammar" (see for example Atkinson 1875),
but judging from the literature I have read, it seems that it was not before the
early 20th century that people began to introduce the techniques for historical
language comparison as a methodological framework.

How this framework became
the framework for language comparison, although it was never really
established as such, is even less clear to me. At some point the linguistic
world (which was always characterized by aggressive battles among colleagues,
which were fought in the open in numerous publications) decided that the
numerous techniques for historical language comparison which turned out to be
the most successful ones up to that point are a specific method, and that this
specific method was so extremely well established that no alternative approach
could ever compete with it.

Biologists, who have experienced drastic methodological changes
during the last
decades, may wonder how scientists could believe that any practice,
theory, or
method is everlasting, untouchable and infallible. In fact, the
comparative
method in historical linguistics is always changing, since it is a
label rather than a true framework with fixed rules. Our insights into various
aspects of language change is constantly increasing, and as a result,
the way
we practice the comparative method is also improving. As a result, we
keep
using the same label, but the product we sell is different from the one
we sold
decades ago. Historical linguistics are, however, very conservative
regarding the authorities they trust, and our field was always very
skeptical regarding any new methodologies which were proposed.

Morris Swadesh (1909-1967), for example, proposed a
quantitative approach to infer divergence dates of language pairs (Swadesh
1950 and later), which was immediately refuted, right after
he proposed it (Hoijer 1956, Bergsland and Vogt
1962). Swadesh's idea to assume constant rates of lexical
change was surely problematic, but his general idea of looking at lexical
change from the perspective of a fixed set of meanings was very creative in
that time, and it has given rise to many interesting investigations (see, among
others, Haspelmath and Tadmor 2009). As a result,
quantitative work was largely disregarded in the following decades. Not
many people payed any attention to David Sankoff's (1969)
PhD thesis, in which he tried to develop improved models of lexical change in
order to infer language phylogenies, which is probably the reason why Sankoff
later turned to biology, where his work received the appreciation it
deserved.

Shared innovations

Since the beginning of the second millennium, quantitative studies have enjoyed a new
popularity in historical linguistics, as can be seen in the numerous papers that have been devoted to automatically inferred phylogenies (see Gray and
Atkinson 2003 and passim). The field has begun to accept these
methods as additional tools to provide an understanding of how our languages evolved
into their current shape. But scholars tend to contrast these new techniques sharply with the
"classical approaches", namely the different modules of the comparative method.
Many scholars also still assume that the only valid technique by which phylogenies (be it trees or networks) can be inferred
is to identify shared innovations in the languages under investigation (Donohue et al. 2012, François 2014).

The idea of shared innovations was first proposed by Brugmann
(1884), and has its direct counterpart in Hennig's
(1950) framework of cladistics. In a later book of Brugmann, we find the following passage on
shared innovations (or synapomorphies in Hennig's terminology):

The only thing that can shed light on the relation among the individual language branches
[...] are the specific correspondences between two or more of them, the innovations,
by which each time certain language branches have advanced in comparison with other
branches in their development. (Brugmann 1967[1886]:24, my translation)

Unfortunately, not many people seem to have read Brugmann's original text in
full. Brugmann says that subgrouping requires the identification of shared
innovative traits (as opposed to shared retentions), but he remains skeptical
about whether this can be done in a satisfying way, since we often do not know
whether certain traits developed independently, were borrowed at later stages,
or are simply being misidentified as being "shared". Brugmann's proposed solution to
this is to claim that shared, potentially innovative traits, should be numerous
enough to reduce the possibility of chance.

While biology has long since abandoned the cladistic idea, turning instead
to
quantitative (mostly stochastic) approaches in phylogenetic
reconstruction,
linguists are surprisingly stubborn in this regard. It is beyond
question that
those uniquely shared traits among languages that are unlikely to have
evolved by
chance or language contact are good proxies for subgrouping. But they
are often very hard to identify,
and this is probably also the reason why our understanding about the
phylogeny of the Indo-European language family has not improved much
during the past 100 years.
In situations where we lack any striking evidence, quantitative
approaches may as well be used to infer potentially innovated traits,
and if we do a
better job in listing these cases (current software, which was designed
by
biologists, is not really helpful in logging all decisions and inferences
that
were made by the algorithms), we could profit a lot when turning to
computer-assisted frameworks in which experts thoroughly evaluate the
inferences which were made by the automatic approaches in order to generate new
hypotheses and improve our understanding of our language's past.

A further problem with cladistics is that scholars often use the term shared
innovation for inferences, while the cladistic toolkit and the reason why
Brugmann and Hennig thought that shared innovations are needed for subgrouping
rests on the assumption that one knows the true evolutionary history (DeLaet
2005: 85). Since the true evolutionary history is a tree in
the cladistic sense, an innovation can only be identified if one knows the
tree. This means, however, that one cannot use the innovations to infer the
tree (if it has to be known in advance). What scholars thus mean when talking
about shared innovations in linguistics are potentially shared innovations,
that is, characters, which are diagnostic of subgrouping.

Conclusions

Given how quickly science evolves and how non-permanent our knowledge and our
methodologies are, I would never claim that the new quantitative approaches are
the only way to deal with trees or networks in historical linguistics. The last
word on this debate has not yet been spoken, and while I see many points critically, there are also many points for concrete improvement (List 2016).
But I see very clearly that our tendency as historical linguists to take the
comparative method as the only authoritative way to arrive at a valid
subgrouping is not leading us anywhere.

Do computational approaches really switch off the light which illuminates classical historical linguistics?

In a recent review, Stefan Georg, an expert on Altaic languages, writes that
the recent computational approaches to phylogenetic reconstruction in
historical linguistics "switch out the light which has illuminated
Indo-European linguistics for generations (by switching on some computers)", and
that they "reduce this discipline to the pre-modern guesswork stage [...] in
the belief that all that processing power can replace the available knowledge
about these languages [...] and will produce ‘results’ which are worth the
paper they are printed on" (Georg 2017: 372, footnote). It seems to me,
that, if a discipline has been enlightened too much by its blind trust in
authorities, it is not the worst idea to switch off the light once in a while.

References

Anttila, R. (1972): An introduction to historical and comparative linguistics. Macmillan: New York.

Harrison, S. (2003): On the limits of the comparative method. In: Joseph, B. and R. Janda (eds.): The handbook of historical linguistics. Blackwell: Malden and Oxford and Melbourne and Berlin. 213-243.

Haspelmath, M. and U. Tadmor (2009): The Loanword Typology project and the World Loanword Database. In: Haspelmath, M. and U. Tadmor (eds.): Loanwords in the world’s languages. de Gruyter: Berlin and New York. 1-34.